The present invention relates to a cooling structure for a multi-chip module and, more particularly, to a cooling structure for a multi-chip module on which a microprocessor and cache memory devices having a large power consumption are mounted.
Conventionally, in a multi-chip module in which a microprocessor and a plurality of cache memory devices are mounted on a wiring board, the power consumption of the microprocessor and cache memory devices is comparatively small. Therefore, a general heat sink having a plate or pin type fins is attached to only the microprocessor, and is forcibly cooled by a cooling fan arranged in an equipment that uses the multi-chip module.
As the semiconductor integrated circuit technology develops, the integration degree and operation speed of the microprocessor increase, and the power consumption also increases. As a result, if only forced cooling achieved by attaching the general heat sink is provided, sufficiently high cooling performance cannot be obtained.
In order to solve this problem, NIKKEI BYTE, No. 155, pp. 150-151, September 1996 discloses a fan-builtin heat sink in which a compact cooling fan is directly attached to the heat sink to cool the heat sink by blowing air to its bottom plate.
As shown in FIG. 5, a conventional cooling structure for a multi-chip module is constituted by a multi-chip module 18 and a fan-builtin heat sink 22. The multi-chip module 18 is constituted by a wiring board 19, and a microprocessor 20 and a plurality of cache memory devices 21 that are mounted on the wiring board 19. The fan-builtin heat sink 22 is attached to the upper portion of the microprocessor 20 mounted on the multi-chip module 18.
The fan-builtin heat sink 22 is constituted by a heat sink 23 and a cooling fan 24. The flow of air generated upon rotation of the cooling fan 24 collides against the bottom surface of the heat sink 23 and flows out to the portion around the heat sink 23. Heat generated by the microprocessor 20 and transmitted to the heat sink 23 is cooled by the flow of air generated by the cooling fan 24. Heat generated by the cache memory devices 21 is cooled by natural convection, or is forcibly cooled by a cooling fan (not shown) separately arranged in the equipment that uses the multi-chip module 18.
In the conventional cooling structure for the multi-chip module described above, as the power consumption of the microprocessor 20 increases, the fan-builtin heat sink 22 having a size to cover the cache memory devices 21 on the multi-chip module 18 becomes necessary. As a result, the flow of air on the cache memory devices 21 is blocked to degrade heat transfer from the cache memory devices 21. When the operating speed of the microprocessor 20 is to be increased, the operating speed of the cache memory devices 21 must also be increased. Accordingly, as the power consumption of the microprocessor 20 increases, the power consumption of the cache memory devices 21 also increases. If the size of the fan-builtin heat sink 22 is increased, as described above, the cooling properties of the cache memory devices 21 are further degraded.
In order to solve this problem, if the wind velocity in the equipment is increased by the cooling fan arranged in the equipment that uses the multi-chip module 18, thus cooling the cache memory devices 21, the noise of the equipment is undesirably increased by the cooling fan. The conventional technique cannot thus cope with an increase in power consumption of the microprocessor 20 and cache memory devices 21.